Lesion-induced NADPH-diaphorase reactivity in neocortical pyramidal neurones.

Pyramidal neurones of the rat neocortex do not normally express NADPH-diaphorase reactivity. However, after stab lesions which extended through the entire depth of the neocortex, strong NADPH-diaphorase reactivity was observed in pyramidal neurones at 7 and 14 days post-lesion. At 3 and 21 days post-lesion fewer and less reactive pyramidal neurones were observed, and no reactive pyramidal neurones were seen at 2 and 26 days post-lesion. The great majority of reactive pyramidal neurones were in layers V and VI and most were situated medial to the lesion. The induction of NADPH-diaphorase implies that the capability to synthesize nitric oxide may be a component of the pyramidal neurones' response to traumatic injury.